Why B5c in US for new links?


#1

Just wondering why anyone would elect to use B5c rather than the integrated unit, since max EIRP in the US with the new OOBE limits is 36dBm, and the B5 radio is going to max at 15dBm with the integrated 25dBi antenna. Unless of course they’ve already got a dual pol dish in place and dialed in.


#2

Antennas work both way. So with a higher gain antenna you increase received signal level at the radio.


#3

Another consideration is that higher gain antennas have narrower beam widths which can help avoid picking up interference.


#4

Thanks—I would think the receive gain would be more important in PTMP scenarios–it wouldn’t alter SNR, but narrowing the beamwidth should. Have to think about whether the added gain, and the increase in RSSI becomes the governing factor in longer links, and whether the SNR changes with link length for a given antenna pattern. I’m not sure the online Design Tool works properly in this regard. And I’m guessing there is no way that it can model the colo interference with multiple B5s on a POP–that would be nice.


#5

Wasn’t really thinking clearly about the link budget, the big dishes obviously make the difference for longer links. But the Design Tool does need a lot of work for proper output with connectorized B5.


#6

In some cases you get higher QAM with lower transmit power.
Also you get more receive gain with a higher gain dish. You have to cutback the transmit power to the proper EIRP, BUT, there is NO limit on the amount of receive gain you can use !